Field
This disclosure is generally related to the field of quantum communication. More specifically, this disclosure is related to a system, method, and device for measuring the optical fiber channel loss in photonic communication.
Related Art
Quantum communication is an information transmission technology for transmitting quantum states from one place to another. Three types of quantum communication currently exist: quantum teleportation; quantum entanglement swapping; and quantum encryption transmission. Currently, quantum encryption transmission—which integrates quantum key distribution with a classic encryption technique—is the only type of quantum communication proven to be secure. Quantum encryption transmission is also the only type of quantum communication that has both practical application and potential for industrialization. Quantum key distribution enables two parties to produce a shared random secret key known only to the parties, which can then be used to encrypt and decrypt message.
Photonic communication is based on the transmission of photons, and can be sensitive to loss on the optical fiber channel. As an example, take quantum key distribution based on the BB84 quantum cryptography protocol, where a sender and a receiver agree on a quantum key. The sender can encode the photon under a polarized state to generate a random sequence, and transmit the encoded photon to the receiver via the optical fiber channel. The receiver can receive and measure the photon based on randomly selected measurement bases. The sender and the receiver can screen the original quantum keys by comparing the measurement bases, which allows both the sender and the receiver to estimate the bit error rate of the transmission process. If the bit error rate is above a predetermined threshold, the sender and the receiver can abandon the key distribution process. If the bit error rate is below the predetermined threshold, the sender and the receiver can determine a shared quantum key. Note that the bit error rate of the transmission process may increase with increased loss on the optical fiber channel. As a result, the rate of code formed to create the quantum key can decrease rapidly, and the quantum key distribution operation may fail to meet the requirements of data encryption and decryption on quantum keys.
Thus, ensuring stability in photonic communication generally requires a high quality optical fiber channel. There is a need to conduct real-time monitoring for the quality of the optical fiber channel and also to optimize the optical attenuation control of the optical fiber channel. However, the characteristics of photonic communication create challenges to meet these needs.
In conventional optical fiber transmission, intense light beams are emitted to the optical fibers. This allows optical fiber losses to be measured directly by calculating the difference between the power transmitted by a sender and the power received by a receiver. However, in photonic communication, isolated photons are transmitted to the optical fibers. This does not allow conventional power measurement based on standard equipment, and also does not provide real-time measurement of the optical fiber channel loss in photonic communication.
Furthermore, during photonic communication, if intense light beans are emitted directly on the optical fibers to measure the optical attenuation, the photon is destroyed in the intense light beans. For example, if the transmission of isolated photons (or “light quantum”) and the emission of intense light beams occur at the same time, a single photon containing key information may be destroyed in the intense light beams. This can result in the receiver being unable to measure the photon, and may also result in a failure of the entire photonic communication.
Thus, there is a need for real-time measurement of the degree of optical fiber channel loss in photonic communication, while avoiding affecting the standard photonic communication and ensuring the correct photonic transmission.